Tanning.



O. W. NANCE.

TANNING.

APPLIOAIION FILED DBO. 27, 1909.

I Patented June 17,1913.

cHABLEs'wEsLEY NANCE, or LoNDoN, ENGLAND.

"ra NrN-e.

Specification of Letters Patent.

Patented June 117, 1913.

Application filed December 27, 1909. Serial No. 535,185.

To all mlwm z't may concern:

Beit known that 1, CHARLES WESLEY 'a subject'of the of Great Britain, residing in London, in the Kingdom of or vaporize. Or,- and particlggrlyin rellar' 1 raising t e.

use Improvements in Tanning, of which than following is a specification.

y hides for the production of leather, and consists in a process hereinafter stated in "detail, comprising essentiallythe 'following steps after the usualfor preliminary ,depilating treatment. .First, ;the hides are immersed in a tanning solution of usual character, in a tankwhich is hermetically sealed against the atmosphere. A high vacuum is then produced in the chamber of about a lb. to the square inch absolutepressure- When the. vacuum reaches this point,"the temperature of the solution is raised momentarily or for a brief will boil,'t at-is, at; or about to Hahn, the temperature "beiiig' preferably kept just. below; the Ipomt at w-hich the tan-' nin'g solution wilhunder like vacuum, boil tively 1 warm weather, instead temperature, the vacuum may"be .-increa sed or made more nearly perfect,'-so thatwater, and it'may-be'the tanning solution itself, will be'thrown-into ebullitlon, and the watercaus ed to vaporize or to pass into steam.

Asa, result of this. treatment, 'water which is 'containedin the pores 'ofthe'hides will .be-causjed to vaporize, andhehcewill force its-way out of the poresby reason of its expansion" and pressure. Thewater vapor, condensing as the temperature or the vacuum is permitted, to fall a slightly, a partial vacuum is created in the pores .of the hides, andthe tanning solution enters to fill the some; The tannin of the solution unites with the gelatin ofthe hide, leaving water behind, and partially occupying the pores. of the hide. The temperatureor the vacuum being again raised, this water is'vaporized, and through repetitions of the process is finally ,completely removed from the pores bf the hides and replaced by tannin, wh ch combines with and converts the hide into leather of peculiarly fine quality.

' -The strength or degree of concentrat on of theitanning solution will vary according to the quality and character of the hide or under treatment, and the solution Erland, have invented certain' new and.

invention relates to the tanning of pleriod to a pointat which water should from time to time be-renewed or replenished, to compensate for the tannin taken up by the hides.

' I-t 1s essential to the economical. carrying out of the process on a commercial scale, and

t0 the production of leather of fine quality, that the vacuum. be high or nearly perfect, and I have found that for good co mercial morre that 1} lb.' to the square inch, the lower the better.; I have also found by :thorou'gh tests, that while the I tanning operation is improved and hastened when carried on in vacuo, the curve representing the decrease in time, which as practically co-incident with the curve of improvement in uality, is a peculiar one, and that a given hi e, whic without .yacuum would take about. fiv-i months totan, will with say 13 lbs. absolute phessure, take abouttwo months or a little working, the absolute pressure shoiil' "be not less; with 10 lbs. absolute pressure, about forty days; with about 4 lbs-absolute pressure, approximately twenty-five days; and with aboutl lb. absolute pressure, approximately twenty days; but with 1} lb. absolute pressure, it can be done in two days.

It will thus be seen that there is a sudden drop at about from 1 lb; to lb. absolute pressure, and this is owing to the fact that at about 9; lb. per square inch of absolute pressure pure water boils at a little lower temperature than the tanning solution, and just before the hide begins to boil, the comparatively pure Water in the pores of the hide boils or vaporizes in advance of the boiling of the tanning solution proper, and with the gases, escapes from the pores of the hide in the form of steam or vapor. "Hence "whemthe liquid in the pores is-reduced to vapor a partial vacuum is formed in the pores, and, when boiling ceases, fresh tan liquor enters to fill the same. This tan liquor inturn similarly acts upon the Walls, of the pores, the tannin being absorbed by the hide, andthe pure water left behind being caused again to boil andthe. remaining gases to be expanded, both being'thus'expelled.

In carrying out,- my. invention I may usev any suita e form of apparatus admitting 'of treatment in themanner above described, bu't'I preferthe apparatus shown in the .accompanying drawings,- wherein:

Figure 1 is aside elevatlo'n of the plant, partially broken away to show the arrange-L ment of the wickerwork separators placed between the hides; Fig. 2, a face view of one of said wickerwork separators.

In these drawings, A and A indicate vacuum pans of usual construction, having removable lids B and B capable of hermetically sealing at times as is customary, and C, C, indicate pulley block devices for lifting the lids, and in case of need, for handling the hides. I

Dindicates an exhaust pipe coupled to the vacuum'pump on the one end and to the tanks on the other, the vacuum pump not being represented in the drawing but merely indicated, as no particular type of pump essential to the carrying out of my process, except it must be one capable of forming a very high vacuum, of which type there are several now existing, nor is any special coir struction of pump claimed herein.

E, E, indicate valves in the pipe D,whereby communication of either or both tanks with the vacuum pump may beshutoff. A further valve may,.of course, be placed between the tank A and pipe D if desired, so as to per mit the two tanks to be handled wholly in dependently of each other, but this being a common expedient requires no special illustration. F indicates a supply pipe for the tanning liquor. Its branches enter the tanks A and A, and the entering ends are preferably brought into fairly close proximity to the inner walls of the tank, so that the liquid escaping therefrom under head or pressure will be broken into fine spray. From the lowest point of each tank extends a discharge pipe for conveniently emptying the tanks when desired. These pipes are respectively furnished with valves H and H, by which they may be opened and closed as required.

J and J indicate glass cylinders, each coupled at its upper and lower ends to one or the other of the vacuum tanks, and designed to receive small pieces of hide which, by reason ofthe communication between the tanks and the cylinder, will be subjected to precisely the same conditions as those in the main tanks. To permit removal of the cylinders J and J for the purpose of examining their contents, the pipes by which they are placed in communication with the cylinders are provided with cocks, as shown in Fig. 1, so that they may be closed while the cylinder is removed.

M indicates a wickerwork mat or separator, ofwhich a suitable number will be provided for each tank. The purpose of these separators is to hold apart individual hides or groups of hides, while permitting the tanning solution to come into contact with every portion thereof, above and below.

Each tank A, A, has its lower portion sinrounded by a water jacket Q supplied by pipes R from the warm water tank T, and

having cocks S by which to open. and close communication between the tank and the water jacket. The purpose of this water jacket is to raise the temperature within the tanks to a point sufficiently high to'beget vaporization of the water contained in the pores of the hides, but not suflicient to injure the hides, and preferably not sufli 'ciently high to produce ebullition of the tanning liquid. If, however, the temperature be not sufficient to injure the hides, and I find that a temperature from to Fahr. is a safe one, slight ebullition of the tanning liquid will occasion no harm, but is somewhat beneficial in that it causes the bubbles of air and gas which tend to adhere to the surfaces of the hides, to be detached therefrom and to rise to the surface of the liquid. There is further shown in Fig. 1' a platform L with steps P by which to reach the same.

Any usual or convenient form of vacuum pan adapted to withstand the high vacuum indicated may be employed, and the provisions for heating may be any of those commonly employed, though I prefer a water jacket or heating coil. Owing to the relatively low temperature, 65 to 70 Fahr., at which water will boil under the high vacuum indicated, application of heat is unnec essary in mild or warm weather, but provi sion is. of course. made for the application of heat whenever the same is required.

The following account of a trial conducted before numerous witnesses for the purpose of testing and demonstrating the procit is to be understood that the test was illustrative merely, and need not be arbitrarily followed in detail in practical commercial working. The tanks being properly supplied with hides separated in the manner indicated, were duly sealed, and the vacuum pump started to produce the desired vacuum. lVhen the vacuum was well advanced, a weak tannin solution was sprayed in a 'ainst the wall of the chamber until the o hides were well covered. The vacuum was increased occasionally up to the boiling point of the tannin liquor. but was not allowed to 'be at this point for more than five minutes at a time. As the tanning liquid gradually evaporated, further weak liquor was run in until the extract was fairly concentrated, after which the liquor was never allowed to boil except momentarily. From time to time a little of the liquor was withdrawn and fresh liquor, preferably unconcentrated, was passed in. After the expiration of two days air was let in, the solution withdrawn, and the hides taken out, asked, and air dried and finished, and were pronounced by experienced tanners present o be better leather than any they had ever tested.

Obviously, the. washing and drying of ess will further illustrate the invention, but

- bark as a separating material between the hldes, and to extract the tannin therefrom the hides may be effected in the vacuum pan,

if desired. So, too, it is not essential to be;

gird produce the solution in the tank, but

tte'r and more uniform results may be atmined-main less time, by introducing a prepared solution of suitable strength or concentration in the first instance, the grids of wickerwork or equivalent material being in such case employed toseparate the hides.

I am'a'ware thatothers have heretofore proposed] to carry on the tanning. process in cacao, and that insome instances high or nearly completeexhaustion has been sug gestedlin general terms,;but.without specify-- in}; the degree of vacuum, or being aware of the sudden decrease in. time required and improvement in quality of leather -produced, as the vacuum rises to about 1} lb. per square inch absolute pressure of vacuum, unobtainable with the old piston air pumps. 80, too, the necessity of maintaining a relatively low temperature, to Fahr. or thereabout, has not hitherto been appreciated, nor has the relation between temperature on the one hand and vacuumon the-other, in its bearing or efiect'upon the tanning solution and upon the leather, been understood or apparently investigated, It-is by reason of maintaining a vacuum so high thatevaporation of the mois'tpre may take place at a. temperature so low as to avoid injury to the hide and the resulting leather, that I am enabled to secure the vastly improved results incident to my process of tanning. 7

Having thus described my inventiom-what I claim is 1. The processof tanning hides, which consists in "placing depilated hides in a tank containing a tanning liquor, thehides being separated by permeable bodies incapable of injuring or being injured by the solution, producing and maintaining in this chamber a vacuum equal toabout lb. per square inch absolutepressure, and maintaining normally in said chamber a temperature below the boiling'point but occasionally raising the temperature for brief periods to the boiling pointin such vacuum.

2. The-improvement in the process of tanning hides, which consists in placing the hides in a vacuum tank, sealingthe same against the atmosphere, produclng a hlgh vacuum in said tank, introducing tanning m the operating vessel, but liquor of any solution in the form of a line divergent spray at a point above the level of the solution until the hides are completely immersed, whereby theair contained in the fresh liquor is liberated, and occasionally for a brief period bringing the temperature to a degree at which the solution will boil in the high vacuum in the exhaust tank, but at no time permitting it to rise'sufliciently high to injure the hides or the resultant leather, but keeping it at or below the ordinary normal temperature. I

3. The process of tanning hides, which consists in immersing the hides in a tanning" solution in a chamber sealed to the atmosphere, reducing the pressure in such cham ber, and maintaining it at about lb. per square inchabsolute pressure, and from time to time soproportioningthe temperature of the liquid and the degree of vacuum that water contained in the hides will be converted into steam, while under the tanning liquor, but without permitting-the temperature torise above 65 to 70 degrees Fahr.

4:. The process of tanning hides, which consists in' placing the depilated hides in tanning solution in a chamber closed to the atmosphere, producing in the chamber a vacuum of about at lb. per square inch absolute pressure, and periodicallv raising the temperature of the tanning solution at this vacuum to a point at which the water will boil, the intervals between such elevations of temperature serving to permit the tannin of the tanning solution in the pores to separate from the water of the solution and unite with the gelatin of the hides, and the successive elevations of temperature serving to convert the free Water in-the pores into steam and thus to remove the water from the pores of the hides.

. 5. The process of tanning hides, which consists in immersing the depilated hides in cHARLEsWEsLEY NANCE.

Witnesses:

WILLIAM REGINALD ORMANnY, HERBERT D. J AMEsoN, 

